The desirability of producing a stereo image to create a 3-D illusion is well documented for a wide range of products and services. These include instrument displays and entertainment. Prior systems for producing a 3-D display have usually been complex, costly, with poor quality image, or require the use of lenses, prisms or filters positioned immediately in front of or worn by the observer.
The phenomenon of stereopsis has long been understood and almost all prior inventions are based upon this principle. In stereopsis, steroscopic vision is accomplished primarily by the interpretation in the brain and the muscle sensation of the converging of the eyes through an angle (parallax) in order to match up the two images of the eyes which see an object from a slightly different angle. Each of the inventions of the past has used this natural phenomenon by providing two planar views (usually photographs) of a common object taken from slightly different camera angles and requiring the two eyes to superimpose these images. The methods for converging these two steroscopic views have included prisms, color separations, polarized filter separations, focused points of observation and real optical images. Modern technology has made available high quality, full color images using video techniques, but not practical technique has been devised to present 3-D video information to the viewer.
One prior art development, the Rickert U.S. Pat. No. 4,322,743 uses a projection optic to focus an image of an object on a "special screen" which has a light concentrating capability, but which does not focus an image. Rickert indicates that the image appears on the surface of the screen. A concave screen such as on a projection T.V., diffuses light rather than focuses light as would be required for projecting an image. A concave T.V. screen can concentrate the light, but cannot focus an image. In Rickert, an image focused on the surface of the screen will be brighest at the radius of the concave screen at the angle of reflection. It may be that Rickert produces such an enhanced intensity image from the concave screen for the left eye on the screen as compared with the intensity of the same image seen by the right eye. If the same procedure is used for the right eye, a moderate stereo effect may result, but it will lack good resolution and contrast.
It is highly desirable to have a 3-D real image projected in space so that it can be observed by a user without special glasses or other aids, with much greater resolution and contrast and without reduction in the brightness of the image. Such a device is particularly desirable where it is relatively low in cost and applicable to a wide variety of 3-D applications.